The fire broke out due to an LPG cylinder leak in the house, the police said.
The residents of the house, unaware of the leak, put pieces of wood in a pot and lit it inside a room to keep themselves warm, and the room caught fire, the police said.
The fire then spread to other parts of the house, a police officer said.
The Station House Officer (SHO) of Town police station, Sunil Kumar, said those who received burn injuries were Ruso Devi, her daughter Rekha Kumari, her grandson Nitish Kumar, and her grand daughter Priyanka.